Been there 13 times and planning to visit next Spring Break.
As a rookie you should sign up at this site:
https://costaricaticas.com/
Find the link to the Sportsmens Lodge and just stay there as the chicas go to their lobby and bar areas and you will have your room. There are safes in the room, breakfast is included in the rate (discount if you join CRT.com too BTW).
Lots of guys for you to meet and mingle to get the lay of the land. Tourism stuff too. They do offer a shuttle service as well. During the day you can explore the sites. Hopefully you speak some Spanish which helps a lot.
Been to a spa in Panama but Costa Rica is closer and easier to get around. They do accept dollars and use cabs with the yellow triangle logo is easy to get around in. Cant speak of other countries but it may be very challenging to figure out. At least Costa Rica is a good starting point. Girls from other countries like Cuba and Colombia do visit too.
SF